Science Achievements of the DEEP2 & AEGIS surveys by Koo, - - PowerPoint PPT Presentation

Science Achievements of the DEEP2 & AEGIS surveys

by

Koo, Faber, and the DEEP & AEGIS Teams

Supported by CARA, UCO/Lick Observatory, the National Science Foundation, and NASA

DEEP2 basics

• Officially finished:

 53,000 spectra  Four fields, 3 square degrees  39,000 with Quality 3 or 4 redshifts  Reliability > 98%

Sampling density on the sky compared to other surveys

Extended Groth Strip Data Sets: DEEP2

Phase I Phase II

EGS is also a CANDELS field.

Color bimodality persists out to beyond z ~ 1

Combo-17 survey:

• 25,000 galaxies
• R-band selected to

R = 24

• 17-color photo-z’s

Bell et al. 2004

Similar results from DEEP2.

DEEP2 and COMBO-17: At least half of all L* spheroidal galaxies were quenched after z = 1

Bell et al. 2004, Willmer et al. 2006, Faber et al. 2007 X4 Back in time ---> <--- Fewer galaxies

 Red sequence continues to grow at late times (Faber et al. 2007)  Only available pool to draw from is the BLUE CLOUD. Hence, galaxies must be moving from the blue cloud to the red sequence due to a decline in star-formation

Formation of the Red Sequence

Theories for Quenching Central Galaxies

External (halo-based) model:

 Massive halo quenching: truncation of “cold flows” and conversion of cold gas to hot halos  Critical halo mass Mcrit ~ 1012 M

(Blumenthal et al.,

Keres et al., Dekel et al., many others) Internal models:  Stellar feedback – starburst  AGN feedback  Secular evolution  Disk instability “Morphological” quenching Possibly driven by mergers

 Quenching is a gradual process that lasts billions of years. It is not a sudden event, as shown by the scarcity of K+A galaxies (Yan et al. 2008)  This is evidence against *sudden* gas evacuation, such as would be caused with AGNs  Quenching starts first in denser environments (Cooper et al. 2006)  There thus appears to be an environment threshold of some kind that begins to be crossed in dense environments around z ~ 2  Massive red-sequence galaxies quench first. These are probably

• centrals. The faint end of the red sequence forms later, via satellite
• quenching. (Bundy et al. 2007, Huang et al., in prep.)
• The central-satellite distinction is important for galaxy evolution.

There is strong evidence for massive halo quenching at z < 1.

What is the quenching mechanism?

Major quenching in high-density environments starts near z = 1.3

Cooper et al. 2006

Yan et al. 2008, following Quintero et al. 2005

Post-starburst galaxies are rare. Most galaxies quench gradually.

Ratio A stars/K stars Emission

Post-starbursts Post-starbursts

U-B

The red sequence appears first at high mass

A new set of photoz’s with 3% accuracy complete to KAB = -20

Huang et al., in prep

Also Bundy et al. 2007, Ilbert et al. 2010, and

• thers

24 mu detected sources in these two panels.

2 4 6 8

Redshift, z Log (Mhalo/M)

15 14 13 12 11 10 9

Quenching first at high mass is consistent with a halo upper mass limit for SFR: Mcrit.

Star-forming band

• C. Conroy, R. Wechsler, D. Croton
• C. Conroy, R. Wechsler, D. Croton

Mcrit

 Peng et al. 2011. See also J Woo talk later this meeting.

 Quenching fraction as a function of stellar mass and local overdensity Massive halo quenching Satellite quenching

 This functional fit matches many trends in galaxy properties vs redshift.  Stellar mass is used as a proxy for halo mass.

Alternative view: quenching is caused by internal galaxy structural properties

U-B

Cheung et al. 2011 using Sersic indices from GIM2D fits by Simard to AEGIS HST images. See also Schiminovich et al. 2007, Bell 2008, Bell et al. 2011, and various Sloan papers.

U-B

Alternative view: quenching is caused by internal galaxy structural properties

Cheung et al. 2011 using Sersic indices from GIM2D fits by Simard to AEGIS HST images. See also Schiminovich et al. 2007, Bell 2008, Bell et al. 2011, and various Sloan papers.

The real variable may be central stellar mass density. Is stellar mass being moved to (or created at) the center? Does this rearrangement of mass cause quenching, or is it merely a byproduct?

Theories for Quenching Central Galaxies

External (halo-based) model:

 Massive halo quenching: truncation of “cold flows” and conversion of cold gas to hot halos  Critical halo mass Mcrit ~ 1012 M

(Blumenthal et al.,

Keres et al., Dekel et al., many others) Internal models:  Stellar feedback – starburst  AGN feedback  Secular evolution  Disk instability “Morphological” quenching Possibly driven by mergers

SLOW!

Bulge building

+

 Star-formation is tightly correlated with stellar mass

• Scatter is <0.3 dex (1-sigma) (Noeske et al. 2007a)

 Abrupt fall-off at high mass corresponds to creation of red sequence  A simple model fits the data after z~3: (Noeske et al. 2007b)

• 1-d family of star-forming trajectories, labeled by stellar mass today
• More massive galaxies have more rapid declines and start earlier

 Thus star-formation is a wave that starts in massive galaxies and sweeps downward to small ones at late times. DOWNSIZING!  Observed scatter matches that of semi-analytic models that include merger-driven SFR! Nevertheless, only a few percent of stars in models are triggered by merger events (Kollipara et al., in prep) Most star-formation is “quiescent” and is well correlated

with stellar mass.

Star formation varies smoothly and predictably

AEGIS: Star-forming “main sequence”

 Star formation declines exponentially in each galaxy  Bigger galaxies turn on sooner and decay faster  Downsizing!

Noeske et al. 2007

τ-model sequence:

Salim et al. 2007

Log Stellar Mass Rapid color change Blue Red

SDSS+GALEX: Similar trend based on absorption-corrected UV flux

satellites

Red, dead, massive Blue, active, small

SSFR based on UV (reddening corrected)

 Major mergers do not increase rapidly back in time (Lotz et al. 2008, in prep)  High-star-forming galaxies are not preferentially disturbed (Kollipara et al., in prep). The pair-enhanced SFR rate is < 2x (Lin et al. 2007)  AGN are found in massive galaxies in blue cloud, GV, and RS (Nandra et al. 2007)  Typical AGN are not noticeably correlated with disturbed galaxies (Pierce et al. 2008) BUT….  “Dry” mergers likely do create pure spheroidals on red sequence  AGN likely are important for “maintenance mode” on the red sequence  High-luminosity QSO phase may be associated with mergers

The role of major mergers and AGN

Mergers do not rise rapidly back in time

AEGIS: Lotz et al. 2008

(1+z)3.4 (1+z)3.4

X-ray AGNs are found in massive galaxies

Nandra et al. (2007)

Pierce et al. 2008

AGNs are NOT preferentially in mergers

 Raw rotation speeds of star-forming galaxies are low on average, but there is a large random component (Kassin et al. 2007)  S0.5 is a theoretically motivated combination of rotation and random motions (Weiner et al. 2006)  Using S0.5 brings all star-forming galaxies to the same Tully-Fisher line, including mergers and irregular-looking objects  This line is the same as the local Faber-Jackson line for spheroidal galaxies

The Faber-Jackson relation (for recent arrivals on the RS)

comes from the TF relation of pre-existing star-forming galaxies

The origin of early-type galaxy scaling laws

Kassin et al. 2007, after Weiner et al. 2006

M* vs S0.5=(0.5Vrot

2+σ2)1/2

M* vs Vrot

The M*-σ4 relation: S0.5 makes sense of pecs+mergers

Raw rotation speed Vrot

Kassin et al. 2007, after Weiner et al. 2006

M* vs S0.5=(0.5Vrot

2+σ2)1/2

M* vs Vrot

The M*-σ4 relation: S0.5 makes sense of pecs+mergers

 Hierarchical clustering is consistent with downsizing if there is an upper edge to the “star-forming band”  A major determiner of a galaxy’s star-formation rate is its dark-halo mass at each redshift. Mergers and disturbances were unimportant  This gives rise to a mass sequence in which a galaxy’s stellar mass today is closely correlated with its past evolutionary history, and thus its properties today  The roots of galaxy scaling relations of many galaxies were laid down during their star-forming phase  Why bulges grow -- and SFR stops – is still a mystery.

Broad conclusions from DEEP2 and AEGIS

Recent and ongoing projects

 Extragalactic background light: Dominguez et al. (2011)

Recent and ongoing projects

 Extragalactic background light: Dominguez et al. (2011)  DEEP3: more redshifts, better environments, rare sources  CANDELS: deep VIJH imaging with WFC3 and ACS  NEWFIRM: photoz’s for z ~ 2 galaxies  Future near-IR spectra with MOSFIRE on Keck

EGS/AEGIS will be a premier field for studying morphologies, structure, and AGN activity of z ~ 2 galaxies